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Leeches help track down endangered species

Bloodsuckers they may be, but who’s to say they can’t be useful too? Leeches store blood from their most recent meal for months, betraying the identity of their prey to those who care to look – which could help find and count endangered species.

Tom Gilbert of the University of Copenhagen in Denmark fed goat blood to leeches in the lab, and found that some of the goat DNA stuck around for more than four months. Next, his team collected 25 leeches from a remote tropical forest in Vietnam which is rich in rare but shy animals.

Four leeches yielded DNA from a rare striped rabbit, one from a rare muntjac, six from a rare badger and three from a rare goat. The team say the rabbit’s presence in the sampled area has been suspected since 1996 but 2000 nights of camera surveillance couldn’t confirm it. The badger and goat DNA is the first confirmation they live in the area.

Gilbert says that at &dollar;5 to &dollar;10 per sample, the method is cheaper than alternatives. And as an added bonus, leeches don’t need to be sought out. “They look for you,” says Gilbert.